1. Field of the Invention
The present invention relates to access control systems, and more particularly to access control system which uses user location information to control access to a restricted area, where the location information is useful to provide more accurate muster and to prevent pass-back.
2. Description of the Related Art
A physical access control system (ACS) includes one or more access controllers which are used to restrict access to one or more restricted physical locations or areas by controlling controllable physical barriers, such as doors, turnstiles, elevators, gates, etc. A “physical” ACS is distinguished from a “logical” ACS which is used to restrict access to data or information on a computer system or the like. Each access controller is configured in any suitable manner for controlling a corresponding controllable barrier to control access to the restricted area, such as including a reader device (e.g., card reader or the like) along with an access device (e.g., door lock or the like). A user presents a token to the reader device, which determines whether the token is “valid” thus indicating an authorized user. If the token is valid, access is granted; otherwise, access is denied.
In a conventional ACS, there is little or no separate tracking of authorized users' locations so that users may leave at any time without further authentication or verification. It may be desired, however, to track which authorized users are located within the restricted area at any given time. It may further be desired to prevent “pass-back” in which one user passes a valid token (e.g., badge) back to another user (authorized or not) to enable both to enter the restricted area using the same token. Pass-back may be defeated or made more difficult by preventing a valid token from being re-used within a certain period of time. A timed non-reuse period, however, may cause inconvenience to authorized personnel. For example, an authorized user might immediately leave the restricted area (e.g., to retrieve a forgotten item from their car) and attempt re-entry within only a short time yet be denied if still within the timed non-reuse period.
A more sophisticated ACS includes authentication upon user exit to more carefully track authorized users located within the restricted area. Such systems often include a “muster” or the like, which is a list or database of authorized users located within the restricted area. In such access control systems, the exit process is similar to the entry process in which the user must present their valid token again to exit the restricted area. Exit authentication, however, presents several problems. A dual access ACS (including exit authentication) is relatively expensive since each entry location must be configured for dual access for both entry and exit. Also, a dual access ACS is often considered inconvenient by, and intrusive to, the authorized users. Dual access systems also require relatively high maintenance since such systems often make mistakes and require occasional reset to ensure accuracy. For example, a user may exit through another door, or through an unauthorized exit or the like, or may simply follow another user out the door resulting in an inaccurate muster. In addition, another person (authorized or not) may follow an authorized user through an entry point without authentication so that security is compromised or the muster is inaccurate. Furthermore, dual access systems limit or restrict the ability to exit the restricted area which may present safety challenges. A dual access system, for example, may prevent fast evacuation of the restricted area during an emergency situation or the like.
It is desired to provide more accurate tracking of authorized users, to defeat pass-back, and to improve muster accuracy of an ACS without the problems associated with dual access systems.